Relativistic study of the electronic structure and 5d orbital of La confined inside a C60 fullerene cage

We determine the electronic structure of the metallofullerene La-C60 for different configurations of La, namely 5d6s2, 5d2 6s and 4f5d6s. The fullerene environment is modelled by a confining potential Vc (r ), equivalent to an attractive spherical square well of depth -8.22 eV and width 1.89 au. The atomic orbitals of La are obtained by solving numerically the Dirac-Fock equations including Vc (r). For both configurations 5d6s2 and 4f5d6s, La donates two electrons to the fullerene molecule, while in 5d2 6s, it is demonstrated that only a partial transfer of the 5d electron to the molecule occurs. For specific values of the well depth, we observe a collapse of the 5d orbital inside the hollow cage region. This phenomenon is interpreted by means of double-valley potentials. (author)